I just got a very very cheap 424! It didn’t power up at first, but after fixing the broken connections at the power jack it is doing fine. The capstan is spinning, but none of the transport buttons seem to do anything at all. It doesn’t even try, it’s like the board with the buttons is disconnected. But it’s not! I’ve opened it up and re-seated the ribbon cables that connect that board but nothing changed. Is ther a chip or cap(s) that tend to go out on these?